I have a 88 cherokee ltd. 4.0 lt. aw4 auto trans that has been acting up lately, after reading several threads on shifting problems (which mine has) tranny shifts normally until engine and tranny warms up,then will not shift into second or thrid gear unless rpm is taken to 3500 and backed off on throttle and no overdrive. I have done a number of repairs to correct the problem . I changed the TPS and adjusted it correctly, adjusted the TV cable, dropped the pan and changed out all the solenoids , new filter and oil . I opened up the 2 large connectors (grey and black) by dip stick tube, cleaned them out with electrical spray , installed new grounds from Battery to engine,engine to tranny,engine to body. installed new ground wire for TCU under dash to a confirmed grounding location under dash. basicly went thru all connectors in engine bay ,opened them up ,cleaned with electrical spray. I inspected and routed some wires that run on top of tranny away from any hard spots, cleaned out all connectors and confirmed proper connection. I disconneted TCU and test drove, tranny will shift if started in first and manually shifting up. the problem has not gone away and I'm at my last resort to change out the TCU. I picked up a TCU from a 91 at a local wreakers, installed it and shifting now happens but, first to second seems to early and still no overdrive. is a TCU from 91 ,compatible with a 88 renix? any suggestions ?

 

Not sure on the compatability.

Is your "trans" switch in Power or comfort mode? If in Power, is the switch lit up?

A bad brake light switch can keep the converter from locking.

 

No numbers on them to compare ? Maybe try detent adjustment .

 

Did you get my message about capitalization yesterday?

 

I have tried both positions on trans. switch and yes it lites up in power mode. I readjusted cable again and test drove with no improvement. also noticed that passing gear or down shift does not work. I will check out brake switch tomorrow. as for the numbers on TCU they are all different, should they be the same besides of the date code?

 

Have you checked to see if your speed sensor is giving the pulses when the wheels are turning? That's my issue. Once trans heats up, the speed sensor stops making the pulses. It is intermittent but it only happens when the engine (and I assume Trans) is warm. Always starts out good in the morning. Hit or miss after that if the Jeep has been run at all.

Here's a good link:

http://www.transonline.com/transdige...ers/index.html

 

mine shifts 1 to 2 right away

 

I think they mixed things up between the years of your XJ and the donor XJ.
There are some shuttle differences between the years iirc. Tranny wise and tcu.
I had transmission issues too. Mine turned out to be mechanical. So I swapped it out.
A way to test whether it's mechanical or electrical is pretty much simply disconnecting the tcu altogether. You should see a code immediately.
Then trying to see if you could shift it manually. You'll skip second but is a good test. I read that you could run indefinitely this way but I just can't see how this couldn't be detrimental to it though.
If it seems to work that way it's not mechanical ; it's electrical. Chasing that down in your year could be tricky.
My 98 had obd2 so I was able to narrow things down some what quickly.
But iirc in your year you can't reset
your ecu. Let alone obtain any freeze data.
But. it will let you know when something is up though when it recognizes it.

I am unsure of this but iirc if you were to turn your key to on off on off (but not enough to hit the starter) and press your odometer rest button your check engine light should start flashing then pause and flash again. Note the number before and after the pauses and search around.
My drunken ramblings are over lol.
I remember my 89 fondly. Good luck man.

 

What year?

Ever refreshed your dipstick ground? That's where the shift point logic circuit grounds and the TCU itself grounds. That's noted in my ground refreshing write-up.
Also, what position do you have the Power/Comfort switch in?

 

Yea Pete, I did my ground's when I waz testing my 02 sensor. Can't you remember EVERYTHING?

Power vs Comfort. For me there was a tipping point. After going 5% taller with 235's, (from 225's), I've left it on Power. It "dogged" some at stock, but the extra did it for me, in power mode now.

Zuk, All I meant was seems to me the AW4 shifts up pretty quick from first. These guys are the real pros^, but mine hits second right away, 11-14 MPH.

 

That's an awfully quick upshift into 2nd. Is it an 87 or something?

 

Truthfully it's 8/89, but 90 sounds cooler, and the only difference might be the C-clips on the axle. Can't you remember EVERYTHING? Shifting feels OK

 

What's the 10th digit in the VIN? K or L?

It's shifting too quickly. I'll bet the trans side of your TPS is bad.

Ever adjust the tV cable?

 

It's an "L". The TPS and the IAC are the only things on my Jeep that have not been checked, not sure I have a speed sensor? My NSS needs adjusted. Right after I finish my winter's wood and come up with another 2K for the suits, I'll be right on that.

 

So it IS a 90. And you thought you were exaggerating all this time. If I've told you once, I've told you a thousand times. Don't exaggerate.

You have a speed sensor.